The invention relates to a device for forming a sheet-metal part having a portion which as an undercut is separately moldable in the device, comprising a press-side ram and a swage and a die which is separately drivable, serves for molding the undercut, and interacts with an undercut contour which is disposed substantially in a filler slide which is rotatably mounted in the swage.
A device of this type is shown and described for example in EP 0 699 489 B1, wherein the rotary slide (rotary cam) shown is rotatably mounted by way of a cylindrical external contour in the swage and/or in a driver. This filler slide serves for configuring an undercut which, in EP 0 699 489 B1, is paraphrased using the term of a “negative angle” in relation to the upper face or external face, respectively, of the formed sheet-metal part. A plurality of dedicated filler slides are provided in order for an elongate and, in particular, arcuate undercut to be configured in/on a sheet-metal part. Each filler slide is disposed in a wedge driver tool (negative-angle forming die) which is disposed in the device described at the outset.
A combination of this type of a device and a wedge driving tool is shown in U.S. Pat. No. 6,523,386 B2, for example. An elastically supported forming ram for shaping the sheet-metal part in a global manner is disposed on the press ram, on the one hand, and a slide which is connected in fixedly driven manner to the press ram and which by way of an oblique guide acts in an actuating manner with the upward and downward movement of the press ram on the die which serves for molding the undercut and which is referred to as an operational slide, wherein the operational slide is infed to the filler slide by way of a swage-side guide of a driver.
Furthermore, U.S. Pat. No. 6,523,386 B2 has a filler slide which is rotatably mounted in the swage or driver, respectively, and which, by way of cylindrical bearing faces which are disposed in a dedicated manner on the circumference, interacts with respectively corresponding support faces which are configured in the filler-slide receptacle in the swage. Support faces which are configured directly in the filler-slide receptacle of the swage require a high-grade material for the swage so as to minimize the wear of bearing and supporting faces which, in particular, are of dissimilar hardness. Moreover, the production of circular-cylindrical support faces is complex and is possible only by using special machines/special tools. Furthermore, a blocking wedge for a locking hook is disposed on this known filler slide, the former by way of a planar support face bracing the blocking wedge in relation to a planar tension face which is disposed in the swage/driver and which serves for rotationally locking the filler slide. The swage-side tension face is disposed so as to be tangential to the circular contour of the bearing of the filler slide, having a tensioning region, lying outside this circular contour, for the blocking wedge.
While the disadvantage of complex production is indeed avoided by an assembly which is known from the abstract of Japanese patent no. 11285740 A and which has bearing faces which are configured in a dedicated manner on the filler slide and has support faces which are configured in a dedicated manner in the filler-slide receptacle in the swage, this is achieved at the cost of expensive manufacturing of the dedicated individual parts which finally also have to be tuned in a complex manner.
Moreover, it has proven successful in the past for structural components of vehicles, such as the A, B, and C-pillars, the roof bow, the side frames, the sills, the longitudinal beams, the transverse beams, etc., to be produced by means of hot forming. Literature also refers to hot-forming processes as form-hardening or press-hardening. The structural components of the body not only play a significant part in imparting stability to the vehicle, but also play a decisive role in terms of safety in the event of a crash. Hot-forming processes lend themselves for addressing the competing targets of reducing the component weight of structural components while maintaining the mechanical key performance indicators.
In order for form-hardened components to be produced, in particular in order for body components to be produced, two methods which are fundamentally dissimilar are known. In the case of direct hot-forming, a sheet-metal blank is heated in an oven to a temperature which lies above the austenitizing temperature of the steel, and is subsequently simultaneously formed and cooled, that is to say form-hardened, in a tool. In the case of indirect hot-forming, a completely shaped and trimmed component of steel is first made from a sheet-metal blank by cold-forming. This component is then heated in a heating plant to a temperature which is above the austenitizing temperature of the steel, and is subsequently form-hardened by rapid cooling in a tool. In both hot-forming methods, the sheet-metal blank or a ready-shaped and trimmed component of steel, subsequent to being heated to the austenitizing temperature, is thermo-mechanically formed in the tool, wherein thermo-mechanical forming is performed at a temperature which is above the austenitizing temperature Ac3 (approx. 830° C.), preferably at between 900 and 1100° C. Cooling down the formed workpieces is performed by means of cooling which is located in a closed tool body. On account thereof, components having particularly superior mechanical properties, in particular having high strength, may be produced. In order for undercut components to be produced, operational slides in combination with filler slides are required in these press-hardening tools (hot-forming tool).
A tool technology having cooled slides and filler slides is described in WO 2011/113621 A1.
German patent document DE 19723655 B4 shows a method for producing sheet-metal products by heating a measured sheet-metal, hot-forming the sheet-metal in a tool pair, hardening the formed product by rapid cooling down from an austenitizing temperature while said product is still held in the tool pair, and subsequent machining of the product.
The invention is based on the object of providing a device by way of which the disadvantages of the prior art may be overcome. It is a particular object of the invention to provide a device by way of which the manufacturing effort for producing hot-formed components may be reduced.
In order for this and other objects to be achieved, a device is provided according to the invention for a press for forming a sheet-metal part having a portion which, as an undercut, is separately moldable in the device. The device comprises a press-side ram and a swage and a die which is separately drivable, serves for molding the undercut, and interacts with an undercut contour which is disposed substantially in a filler slide which is rotatably mounted in the swage. The filler slide is transferable from a molding position to a position which exposes the undercut in the sheet-metal part, and vice-versa. Furthermore, at least one temperature-control installation by way of which the filler slide at least in portions is capable of being temperature controlled may be provided in the filler slide. By providing temperature-control installations, the filler slide which is configured as a rotary slide may be used in a hot-forming tool for producing hardened components.
Moreover, a plurality of temperature control installations by way of which individual portions of the filler slide are capable of being temperature controlled to dissimilar or identical temperatures may be provided. When these temperature-control installations are impinged with dissimilar temperatures, a further benefit is achieved in the region of the rotary slide in that what are referred to as soft zones (tailored tempering) may be generated in the component by way of the dissimilar temperature zones in the slide region. Soft zones are achieved in those regions in which comparatively warm temperature-control installations are provided, since the component is cooled down less rapidly in these zones.
The temperature-control installations in the longitudinal direction of the filler slide can be disposed sequentially. On account thereof, zones which, in the longitudinal direction of the undercut region of the component, are in sequence may be generated having dissimilar mechanical variables, in particular in terms of strength and/or ductility.
Additionally or alternatively, the temperature-control installations may be disposed beside one another. On account thereof, zones having dissimilar mechanical variables may also be achieved in a transverse manner to the longitudinal direction of the undercut region of the component. The degree of freedom in arranging the zones with dissimilar strength and/or ductility is thus enhanced.
The ducts may be disposed so as to be substantially mutually parallel. Advantages in the manufacturing of the filler slide result therefrom.
Furthermore, the ducts may be aligned so as to be substantially parallel with a rotation axis about which the filler slide is rotatable.
According to a first embodiment of the invention, the temperature-control installation may be configured as at least one duct through which a temperature-controlled medium flows, in particular a gas and/or a fluid. Temperature-control of the rotary slide by means of a gas or a fluid offers the advantage of continuous temperature-control, wherein the temperature in the respective portions of the rotary slide may be maintained in very constant manner.
In a second embodiment of the invention, the temperature-control installation may be configured as at least one depression in the shape-imparting surface of the filler slide. The shape-imparting surface of the filler slide is a face of the slide which comes into contact with the sheet metal to be shaped. By configuring a depression, an air gap between the sheet metal and the filler slide is enclosed when the sheet metal is being hot-formed. This air gap serves as a local thermal insulator, preventing rapid cooling of the local region, wherein soft regions in the sheet-metal part are implemented by this portion.
In a third embodiment, the temperature-control installation is configured as at least one electric heating cartridge. Electric heating elements offer advantages in that they are capable of being rapidly set to the desired temperature. Moreover, the temperature may be controlled and/or regulated in a very accurate manner.
However, the embodiments which have been described above may also be combined with one another such that a plurality of temperature-control installations of dissimilar design are capable of being combined in one rotatable filler slide.
Water, coolants, oil, emulsions and/or combinations thereof are suitable as a medium.
Furthermore, the filler slide which is rotatable between a molding position and a position which exposes the undercut in the sheet-metal part may be supported in relation to corresponding support faces in the filler-slide receptacle in the swage by way of bearing faces which are circumferentially disposed, wherein the filler slide is configured having bearing faces which have a flat planar design and which toward the end of a rotation movement of the filler slide from the exposing position to the molding position land on support faces which are of a likewise flat planar design in the filler-slide receptacle. The advantage of planar bearing faces and of planar support faces lies in the absence of friction-based contact between the corresponding faces in the event of rotation of the filler slide, on account of which wear on these faces is avoided.
Substantially non-contacting landing, without wear, of a bearing face on an associated support face in a design embodiment of the invention is achieved in that the bearing faces of the filler slide in the rotation direction toward the molding position are, in each case, delimited by a radial line which emanates from the rotation axis of the filler slide, each radial line with a respective bearing face forming at least a right angle (90°).
Non-contacting landing without complex tuning measures in a further advantageous manner is achieved in that the filler slide for the flawless planar interaction of the bearing faces thereof with the corresponding support faces on the swage side has a rotary guide which either has a predefined enlarged clearance in the bearing, or which according to further proposals is equipped with a radially resilient elastic intermediate element, preferably in the embodiment of a rubber bush or of a corrugated sheet-metal bush of spring steel. A rotary guide of the filler slide which is disposed so as to be eccentrically disposed in the direction of the swage-side support faces and which by the way is capable of being combined with the aforementioned assemblies is also contemplated.
Depending on the number and on the reciprocal angular positions of the bearing faces and support faces, it is provided with a view to the aforementioned assemblies for fixing the filler slide for configuring a flawless undercut that the filler slide in the molding position is locked in a rotationally fixed manner to the swage, specifically in the radial and/or axial direction.
In a refinement according to the invention, an axle which penetrates the filler slide across the length thereof and which, on the swage side, is fixedly disposed is possible as the above-mentioned rotary guide for the filler slide, on the one hand, or fulcrum pins disposed at both ends of the rotary slide for mounting in static bearings provided on the swage side are possible. Instead of the resilient rotary guides mentioned above, these static bearings by means of an elastic intermediate layer may be disposed so as to be movable in the direction of the support faces which are disposed in the filler-slide receptacle.
In a development of the filler slide, it is furthermore proposed that the filler slide is formed from a cast-iron alloy, cast steel or gray iron, from tool steel, or from a steel alloy having copper material, and that the bearing faces and the swage-side support faces are configured separately on hardened strips or strip portions from a case-hardened steel.
Instead of the landing technique of the bearing faces on the support faces, described above, by means of slightly displaceable filler slides, it is also possible for the support faces to be provided on pistons which are disposed in the swage so as to be hydraulically controlled and lockable and which impact on the bearing faces which are disposed in the molding position of the filler slide.
A further proposal relates to the die, which serves for molding the undercut, to be provided as an operational slide in a wedge-driver tool that has been described at the outset. The operational slide is movable in relation to the filler slide by way of a slide bed which is moved on the ram side and by way of a driver which is at least in portions disposed in/on the swage.
The actuation of dies by wedge-driver tools in the case of a plurality of filler slides which are disposed in particular in an arcuate manner in a press device for molding an arcuate undercut may instead be provided in that the dies are driven separately from the press-ram movement, for example by way of piston/cylinder units which are effective in a hydraulic or pneumatic manner.
Further advantages of the invention are to be mentioned in a summarizing manner hereunder. The present crash-related requirements which are set for the vehicle body in particular in the loading event of a side impact, for example in the case of the B-pillar reinforcement component, may be implemented by the above-described device by zones having dissimilar strength in a component. The so-called soft zones (tailored tempering) are presently produced by particular tooling techniques (air gap, heating cartridges) in the cooling process within the tool, or are implemented by external process steps outside the hot-forming tool (oven technology with dissimilar temperature zones, subsequent annealing of the component). The soft zones in regions having an undercut can only be produced within the tool by using the filler-slide technology method described above. A rotary slide having integrated zonal cooling has, inter alia, the following advantages:                minor space requirement; smaller tools may be constructed on account thereof;        comparatively less constructional effort than the combination of two slides (forming slide and filler slide), on account of which the economic efforts may be reduced;        using regional cooling in a rotary slide, a component having soft zones also in the region of an undercut geometry is possible;        rotary slides are not only suitable for hot-forming steel but also for materials such as aluminum and magnesium.        
The invention is described by way of device for a press for forming a sheet-metal part having an undercut, which in the drawing is shown only in portions, and by way of a filler slide which is illustrated in the cross section.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.